Load-distributing arrangement for tractor-trailer combinations



M. D. KOONTZ LOAD-DISTRIBUTING ARRANGEMENT FOR TRACTOR-TRAILER COMBINATIONS Oct. 12, 1954 3 Sheets-Sheet 1 Filed June 16 1950 III I I5. I Wm [I I I I W 3 SheetsSheet 2 M. D. KQONTZ LOAD-DISTRIBUTING ARRANGEMENT F OR TRACTOR-TRAILER COMBINATIONS Oct. 12, 1954 Filed June 16, 1950 inventor WWW/0.160 M (It omega Patented Oct. 12, 1 954 LOAD-DISTRIBUTING GEMENTj'FOR TRACTOR- TRAILER; GOMBI'NATIONS Marshall D. Koontz, Detroit, Mich.

AppIication'JuneIG, 1950, serialNo. 168,530

-5 Claims. 1 This invention relates to tractor-trailer vehicles and, in particular, to load and traction equalizing arrangements for suchvehicles.

One object of this invention is to-provide a load-distributing arrangement for tractor-trailer vehicles whereby the load of a semi-trailer may be adjusted relatively to the tractor or towing vehicle so as not only to lighten the load applied by the semitrailerto the coupling-device between the vehicles but also tovary 'theload distribution between the front and rear wheels of the towing vehicle or tractor and consequently tovary the traction exerted by the dilferentwheels.

Another object is to provide a load-distributing arrangement of the foregoing character'for tractor-trailer vehicles wherein the arrangement prevents jack-knifing or nose-diving of the tractor or towing vehicle andimprovesthesteering qualities of thelatter vehicle by enabling more of the load to be transferred from the rear wheels to the front wheels thereof.

Another object is to provide a load-distributing arrangement of the foregoing character for'tractor-trailer vehicles whereinmechanism is provided for exerting a pull uponthe rearward' end of the towed vehicle or semi-trailer, the tension element being connected to a point intermediate the front and rear wheels of the towing vehicle or tractor so as to lighten the load 'otherwise exerted on the coupling device between the vehicles.-

Another object is to provide a load-distributing arrangement of the foregoing character for tractor-trailer vehicles wherein mechanism is also provided for braking the tension element so as to restrain its motion.

Another object is to provide a load-distributing arrangement of the foregoing character for tractor-trailer vehicles wherein the tension element is also provided with one or more compensating springs and also preferably with an adjustment by which the force of the compensating springs upon the tension element may-be varied.

Another object is to provide a load-distributing arrangement of the foregoing character for tractor-trailer vehicles wherein the load proportionately sustained by each wheel of the towing vehicle may be adjusted to satisfy maximumload requirements of State highway laws.

In the drawings:

Figure 1 is a top" plan view, with the towed' vehicle partly broken away, of atractor-trailer combination equipped with the-load-di'stributing and traction-adjusting arrangement, according toone form of the invention;

Figure 2 is a side elevation'of-the tractor trailer upon the coupling between the vehicles.

2 combination shown in Figure 1, with the tractor or towing vehicle partly broken away;

'Figure 3 is a. cross-section taken along the line -3'3-'in- Fig-ure 1, showing details of one of the equalizing springs;

Figure 4 is a top plan viewof amodified loaddistributing arrangement for a tractor-trailer combination, with the bodies of the towing and towed vehicles removed;

Figure'5 "is a view similar to Figure 4, but showing a further modified load-distributing arrangement for a tractor-trailer combination;

Figure 6 is'a top plan view of a commercial tractor-trailer combination equipped with the load-distributing arrangement of this invention,

with the cab and floor of the tractoromitted;

Figure '7 is a side elevation of a commercial tractor-trailer combination'shown inFigure 6; and

Generalarrangement Hitherto, the operation of towing vehicle or tractors towing heavy loads has been unsatisfactory and frequently dangerous, particularly where the load beingtowed' is a semi-trailer or twowheeled vehicle having the weight of the forward portion thereof overhanging and pressingdown Since the wheels of such a trailer or towed vehicle are often located rearwardly of the center of the towed vehicle, the load is not'balanced equally on opposite sides of the axle but is considerably greater toward the forward end of the towed vehicle. This preponderant load is concentrated upon the coupling device between the towing and towed vehicles and consequently presses downward upon the rearward end-of-the towing vehicle, tending to raise the forward wheels thereof off the ground around the center line of the rear axle as a fulcrum. This action in turn not only causes a disproportionate amount of the load to excessive amount of the load upon the rear wheels of the towing vehicle often forces the owner to install a set of helper springs to counteract the sagging at the rearward end of the towing vehicle. This imbalance or excessive weight upon the rear axle causes accelerated wear upon the rear tires. If there is also a slight difference in air pressure in the tires of the towing vehicle under these conditions, a tendency for the towing vehicle to weave, whip, or oscillate sidewise occurs which is transferred to the towed vehicle, often in a multiplied manner, thus creating a trafiic hazard. Occasionally, the coupled vehicles even jack-knife under such circumstances, causing a wreck.

The installation of a dolly or similar device under the front end of the towed vehicle or trailer, while previously used in an effort to reduce these difficulties, although assisting travel in a forward direction, complicates or restricts the drivers ability to back the vehicle properly. Finally, the concentration of load on the rear wheels of the towing vehicle or tractor often brings the driver into conflict with State laws which limit the weight which each wheel may exert upon the highway, and under such circumstances drivers occasionally lose much valuable time in arranging and redistributing their cargo in the trailer in the effort to reduce the excessive Weight and to comply with such State laws.

The present invention eliminates these diniculties in a simple and effective manner by connecting the rearward portion of the towed vehicle to the intermediate or forward portion of the towing vehicle by a flexible tension member, such as a cable or chain, in such a manner as to exert a strong pull between these points remote from the coupling device between the vehicles. The result is that the load on the rear wheels of the towing vehicle is reduced and that on the front wheels thereof increased, thereby giving better traction to the front wheels, with consequently improved steering. Jack-knifing and weaving or yawing of the vehicles is thereby eliminated, and tire wear on the rear tires of the towing vehicle greatly reduced, State laws are thereby readily complied with, and the forward tires of the towing vehicle are made to bear their proper share of the load. If the towing vehicle is power-driven at its front wheels as well as at its rear wheels, the invention increases the efliciency of the vehicle by increasing the traction which the front wheels are able to exert on the road. Steering is also greatly improved. In some of the drawings, a part of the forward portion has been omitted to conserve space.

First form of a load-distributing arrangement Referring to the drawings in detail, Figures 1 to 3 show one form of the load-distributing arrangement of the invention, generally designated id, as applied to a towing vehicle l i and a towed vehicle i2, such :as a trailer, the vehicles 1! and l 2 being hitched together by means of a coupling device, generally designated 3. The towing and towed vehicles H and i2 and their coupling device it are generally conventional and their .etails are therefore beyond the scope of the invention, except as they enter into the action of the load-distributing arrangement it. The towing vehicle H has the usual frame it with front and rear axles I5 and it; provided with front an: rear wheels I! and i8 and a body, generally des-- ignated is of any suitable type. One half of the coupling device i3 is mounted upon an arm or bracket 2i secured to the rearward end of the frame it, whereas the other half 22 of the coupling device it is mounted upon the forward end of a bracket 23 mounted upon the forward end of the frame 2&- of the towed vehicle or trailer it. Mounted on the trailer frame 213 are springs 25 carrying the axle 25, the outer ends of which carry ground wheels 2'1 A body 23 is mounted upon the frame 2 1 and may be of any suitable form.

The rearward end of the trailer frame 24 carries a depending cross member 3!} having latorally spaced bores 3; in which are journaled screw shafts 32, the rearward ends of which carry hand cranks 33. The threaded portions of the screw shafts 32 are threaded into threaded bores 34 in the rearward ends of rectangular frames or tie structures 35. The forward ents of the frames 35 are smoothly bored as at 36 to slidably receive connection rods 3'? which are encircled by compression springs 33 arranged between the forward ends of the frames 35 and heads 33 on the rods 33'. Each rectangular frame 35 is slidably mounted in parallel guide-ways ii) (Figure 3) formed in approximately parallel members at extending downward from base plates 12 bolted or otherwise suitably secured as at 33 to parallel longitudinal channel members (it forming a part of the trailer frame 24. Secured to eyes at the forward ends of the rods 31 are the looped rearward ends of cables or other flexible tension members 436 which are separably connected as at i! to the rearward ends of a flexible tension member or cable it arraged in an approximately U- haped path and having its rearward portions passing through bell-mouthed tubular guides 49. The rearward ends of the guides 9 are preferably located substantially in a vertical plane passing through the coupling l3, in order to minimize strain upon or stretching of the tension members it, "is in executing a turn, and consequently to prevent jack-lmlfing of the vehicles in executing such turns. The guides 59 are supported by struts 5a and 5! depending from the tractor vehicle frame it, the struts 5| extending downward from a cross member 52. Also mounted on the frame it intermediate the front and rear axles iii and it is a cross member 53.

Mounted on the cross member 53 and extending downward therefrom are pivot shafts or stud 5t and 55 (Figure 1) spaced apart from one another in a lateral direction. Mounted on the pivot shafts E i and 55 are drums 5t and El respectively, these being preferably grooved at their peripheries to receive the cable at. The drum is encircled by at least one complete turn of the cable 38 in order to cause the cable to tightly engage the drum 5:? (Figure 2). Connected to the drum 56 is a brake drum 53 which is engaged by a brake band 59, one end of which is suitably anchored as at 653 to the cross member 53 and the other end of which is connected as at iii to suitable conventional brake-operating mechanism, generally designated 52 (Figure l) which extends upward into the cab or drivers compartment of the towing vehicle I! so as to enable the brake 59 to be applied or released, as desired.

In the operation of the first form of the invention, the operator loads the trailer or towed vehicle i2 as heavily as is desired or feasible. Due to the great overhang of the forward end of the towed vehicle I2, in the absence of the load-distributing arrangement 10 of the present inven- "and "4at Iponen't of force to the struts 50, 5|, counteracting thejdownwardthrust of the load upon thecouovercome.

without halting the vehicles, replacing the fixed cross member 53 by a slidable Fr Ab "uremic ass-thee a a a pee of "this glee-15 heeee transferred through the bracket 'l'ifalhd eeupfieg device 13 .to thebracket 2| and rearward end not i v le l'l'tben'gage the ground orroad G with "an exe siveforce, but also tends'to'pushthe rearwardens -of ,theframe l4 downward around the rear,,aX1e l6 as a fulcrum, causing the forward endof thefraine I4 and consequently the front 'aiiile l5 torise. This lessens the grip of the front w; eels ll 'u'p'on the road G and "creates the hazardous conditionpreviously referredto. H I"o 1 "edistribute'the load so asto place more of it .j .u' Q t ef p ls 1 a d educ t e p l pq "rear wheels [8, the' operja'tor rotates the screw I tsj3f2 'bjy means of the cranks 33 in'order to apply ten's ion to the flexible'tension members 46 This tension applies a vertical com- ,pling I3. The'greater the tension appliedto the flexible tension members 46 and '48, the greater is the proportion of the load applied to the front wheels Hand subtracted from the rear wheels l8. This action resembles thatof a truss, dueto the 'angularity of the portions of the tension mem- "bers 48 on the opposite sides of theguides 49. The

rectangular frames 33 of course slide longitudinallyfinthe guideways 40 (Figure 3) when the screw: shafts 32 are rotated, and the'compression "springs 38 provide a cushioning effect which absorbs road shocks and equalizes the tension on opposite ends of'the flexible tension member 48,

as transmitted by the flexible tension member 46.

In driving the tractor-trailer combination formed by the towing vehicle II and the towed vehicle l2 with the load-distributing arrangement under tension in this manner, the operator 'fin'ds'that steering is greatly improved due to the greater traction obtained by the front wheels ll upon the ground or road G and he also finds that he 'is'able to stop his vehicles in a shorter space 7 due to the increased e'fli'ciency of his front wheel brakes brought about by the increased traction -of his front wheels H. Jack-knifing'of the vehicles, nose-diving of the forward or towing vehicle are found to be completely corrected and By thus suitably manipulating the hand cranks 33 and screw shafts'32, the operator can also redistribute the load upon the wheels of the towing vehicle II and thereby comply more easily with "State laws governing 'thema'ximum permissible load tobe applied by each wheel. By

applying the brake 59 by the brake operating mechanism 62, the operator can instantly snub any tendency of the vehicles [I and [2 to jack- 'k'nife.

Second form of Zodddz'strz'butz'ng arrangement ,QIHeSeQQnd form of load-distributing arrangement generally designated 10 (Figure 4) is for "thernostp'art identical with the load-distributing larra'ngement ID, and similar parts bear similar;

,reference' numerals. The load-distributing ar- .frailgemerit 10, however, is additionally provided withmeans for tightening the tension members 46 and 48 from the drivers seat while under way member 6 9 the opposite ends of which are slidably ,n' ountedin longitudinal guideways H (Figure 4).

'l hejslidable nemberBB is reciproeated toand thej s nrw 10f a recin oc blefh'ye *1 75 "same way.

'inot'or 13'having'a'double aetinghydraulie This consists in of,the towingvehicleframe I4. This pressure hmyjeafi'eee the rear wheels T8 of the towing TM pressureifluidfrom a supply pipe 82.

, a'gain'stjwhich the sbringsSS abut.

having fixed heads 39' as; in F ig'ures ,l, and 4, the rods 31of Figures are threadedas atlfltandproable "1;

fi t'eii ires 13 l; hfe melt Pr s ur flui'dis transmitted-to either 'ofthe oppositeends "WT- 0 19 1 'ventional design e which -p ressure fluid is supplied by t e pipe is' -eohheeted to e eehv htiehei The eperatieh hr theload-distribiiting arrangement 10 shown in Figure 4 is generally slimilarto that of. the ,loaded s ii u ne a an ement. shown in"Figures1 ths'irlemsive'tvith eer'tain'a'ddition s, 'Ifhese additions are that by manipulatcross member "53' can be moved forward or rearare, thereby tightening or 1eesen1ng the flexible jtension'inembers 46 and. In thisihahher, the

load proportionatelycarried by eachpair of wheels can be adjusted instantly from the 'driversseat whi lejun'derway to shit varying conditions of operatio'n, Thebrake saihperat e'h thehydraulic motor 62 .is control ed by moving the handle "34 'of jthe control. valve 8! to apply'j'or release the brake, as 'jdesiredftojaccomplish the resultsset r thjm the descriptionjof the eperati'oniof the "first form "of load-distributing arrangement.

Third mm of [bad distributing arrangement ,lf i e r filiibl i e. a ran ement era y d n e 9 b wnin Figure 1 simi ari nciple to the load-distributing arrangement 10 shown in Figure 4, except that the positions of the flexible tension members "46 and 48 are; reversed, Since the individual elements are generally similar, -however,;they are designated with the same reference num'erals where substantial identityexists. II n Figure 5, the cross member "l6 and ;are of course greatly lengthened in orderto extend from the rearward end of the towed vehicle 12 to the forward end of the towing "vehicle ll where the drivers seat is located. In I order to pefrn'iitffreere ativemotion between the towihgandftowed vehicles I and I2, flexible con- .dui'ts =9 .92 endissier mterbesea in the hydraulic fluid eoriduits 12, 1s andftw respectivelyat the locations at'lthe portionsthereof extending between'the adjacent ends of the two vehicles ll anall p it he rodsf3l, moreover, "to which theloop Tends 4510f the flexible tension. members "46 are connected pass through holes Mina cross member Instead of vided with movable heads 4 $1, the positions of which are adillstedby moving the. nuts Slate and fro"along the threaded portions 96,1there'by adju's ting flthe -force ekert'ed by the compression s'mings"'38. d 'adjustinggscrewshafts13 2 andhand cranks 33 are Hpm e The reeta i larframes s5 and their WiHibe a ent he?theses m h 1 ents could also be'o'mitte'd from Figure 4 in the The operation of the third form of the invention shown in Figure is generally similar to that of the second form shown in Figure 4, except that on the manipulation of the control handle 83 of the control valve l8, pressure fluid is admitted from the supply pipe 79 to the service pipe '12 to move the slidable member 69 forward and slacken the tension members "is and 48, whereas the admission of pressure fluid to the service pipe Iii moves the slidable member t9 rearwardly and increases the tension on the flexible tension members it and 48. The brake 59 is operated in the same manner as in Figures 1 and 4 and for the same purpose.

Fourth form of load-distributing arrangement The fourth form of load-distributing arrangement, generally designated Hit shown in Figures 6 and 7 substantially applies the second form if! of Figure 4 to a commercial highway tractor and semi-trailer, generally designated It! and 1132 respectively with only minor differences. Consequently, the same reference numerals are em ployed for the component parts of the arrangement 96, as in the arrangement it. The tractor till, which is shown merely diagrammatically since any tractor may be used, consists of a frame its having paired front and rear wheels 1M and 1535 respectively, and a so-called fifth wheel, generally designated Hi6, mounted on the upper rearward side of the frame I63. Ihe fifth wheel [36 has a base it? carrying transverse pivots or trunnions I08 upon which the tilting table N39 with its inclined ramp H8 is tiltably mounted. The table ms is provided with a central slot III with a flared or diverging entrance portion l 2 for receiving the usual kingpin H3 which projects downward from and is secured to the kingpin supporting structure I it secured to the lower forward side of the frame i 25 of the semi-trailer H32. The trailer body HE is mounted on the frame I I5, partly on cross members i i? at the rearward portion thereof, the forward portion being bent upward to a higher level as at lit in order to accommodate the kingpin supporting structure 1 i i.

The operation of the fourth form of load-distributing arrangement we is substantially the same as that of the second form shown in Fisure 4, with the exception of the different manner of coup-ling the two vehicles (91 and M2. The coupling and uncoupling procedure, however, is the same as that followed in conventional tractor-trailer operation and as it is well-known to those skilled in the tractor-trailer art, requires no detailed description. Just as in the case of the other forms of the invention, it is of course necessary to uncouple the separable connection til between the flexible tension members 45 and A8 before uncoupling the semi-trailer me from the tractor ESL It is, of course, assumed that the semi-trailer I82 near its forward end is equipped with a suitable movable prop in order to support the forward end when the vehicles are uncoupled. Such props are well known and the showing of the prop has been omitted so as to simplify the illustration of the load-distributing arrangement 109.

For convenience and conciseness, the words tractor and trailer or semi-trai1er have been used in the specification and claims of the present application to denote the towin vehicle and towed vehicle or implement, respectively. It will be understood, however, that the term tractor includes any type of towing vehicle and not merely the commercial highway tractor used in hauling semi-trailers.

Fifth form of load-distributing arrangement lhe fifth form of load-distributing arrangement, generally designated H (Figure 8) is generally similar to the first form Of the invention shown in Figures 1 to 3 inclusive, except that the mechanical adjustment for altering the tension on the cables t6, it is placed forwardly of the semi-trailer axle and is controlled and adjusted from the forward end of the semi-trailer. Consequently, the same reference numerals are employed for the component parts of the load-distributing arrangement lit as are employedforthe load-distributing arrangement it, except where they differ in details. In the load-distributing arrangement 20, the rectangular frames 35 and their guideways 46 are generally similar in construction to those shown in Figures 1 to 3 inelusive, and similar rods 3'? with heads 38 carry similar helical springs The cables 46 are similarly connected at 5 to the rods 37 which similarly pass through bearing bores 36 in the forward ends of the frames 35 and have similar separable connections i'l with the cables 38. Instead of the frames 35 being pulled backward by the screw shaft 32 and cranks 33, operating in threaded portions 3d of the frames 35, from the rear of the semi-trailer, the frames 35 01" the loaddistributing arrangement 26 are pushed backward by screw shafts l2i threaded through threaded bores E22 in brackets i213 depending from the frame 2 3. The rearward end 213 of each screw shaft l2l abuts the forward end portion 255 of each frame 35 so as to push it backward or permit it to move forward as the screw shaft :25 is rotated. Couplings 25 connect the screw shafts iEl to operating shafts fill, each shaft l2? being rotatably mounted in a bore I28 in a bracket I29 depending from the forward end 01" the semitrailer frame 2%. A hand crank I30 is mounted on the forward end of each operating shaft I27 and the shafts 12? preferably carry graduations I3! thereon.

The operation of the fifth form 5233 of the invention (Figure 8) requires no additional explanation over that set forth above in connection with Figures 1 to 3 inclusive, except to say that turning the cranks 13% in one direction pushes the frames backward so as to compress the springs 32 and consequently tighten the cables 46, 33. Turning the cranks I30 in the opposite direction permits the springs 33 to push the frames 35 forward, loosening the cables 46, 48. The graduations i3! indicate the amount of motion obtained and consequently indicate the tension obtained on the cables 25, Q8. The cranks 36 at the forward end of the semi-trailer 12 in Figure 8 are more conveniently located than the cranks 33 at the rear of the semi-trailer E2 in Figure 1, since the driver does not have to go to the rear of the semi-trailer in order to make the adjustments. It is advisable in Figure 8 to have the points of attachment of the cable 46 located rearwardly of the center of gravity of the semi-trailer so as to obtain the proper distribution of force.

What I claim is:

l. A load-distributing arrangement for tractor-trailer vehicles interconnected by a coupling wherein each vehicle has a coupling end adjacent said coupling and a remote end remote from said coupling, said arrangement comprising a pair of laterally-spaced flexible tension member anchorages mounted on one of said vehicles at a location nearer its remote end than its coupling end, a guide wheel carrier mounted on the other vehicle at a location nearer its remote end than its coupling end, a flexible tension member guide wheel means rotatably mounted on said carrier, and a flexible tension member disposed in an approximately U-shaped path along said vehicles with its free ends secured to said anchorages, said flexible tension member having substantially parallel portions extending from said anchorages along opposite sides of said vehicle and a connecting portion extending between said parallel portions to and around said guide wheel means.

2. A load-distributing arrangement for tractortrailer vehicles interconnected by a coupling wherein each vehicle has a coupling end adjacent said coupling and a remote end remote from said coupling, said arrangement comprising a pair of laterally-spaced flexible tension member anchorages mounted on one of said vehicles at a location nearer its remote end than its coupling end, a guide wheel carrier mounted on the other vehicle at a location nearer its remote end than its coupling end, a flexible tension member guide wheel means rotatably mounted on said carrier, a flexible tension member disposed in an approximately U-shaped path along said vehicles with its free ends secured to said anchorages, said flexible tension member having substantially parallel portions extending from said anchorages along opposite sides of said vehicle and a connecting portion extending between said parallel portions to and around said guide Wheel means, at least one of said anchorages being movably mounted on its respective vehicle, and resilient means yieldingly engaging said movable anchorage and urging said movable anchorage in a direction adapted to tighten said flexible tension member.

3. A load-distributing arrangement for tractor-trailer vehicles interconnected by a coupling wherein each vehicle has a coupling end adjacent said coupling and a remote end remote from said coupling, said arrangement comprising a pair of laterally-spaced flexible tension member anchorages mounted on one of said vehicles at a location nearer its remote end than its coupling end, a guide wheel carrier mounted on the other vehicle at a location nearer its remote end than its coupling end, a flexible tension member guide wheel means rotatably mounted on said carrier, a flexible tension member disposed in an approximately U-shaped path along said vehicles with its free ends secured to said anchorages, said flexible tension member having substantially parallel portions extending from said anchorages along opposite sides of said vehicles and a connecting portion extending between said parallel portions to and around said guide wheel means, both of said anchorages being movably mounted on their respective vehicle, and resilient means yieldingly engaging said anchorages and urging 19 said anchorages in directions adapted to tighten said flexible tension member.

4. A load-distributing arrangement for tractortrailer vehicles interconnected by a coupling wherein each vehicle has a coupling end adjacent said coupling and a remote end remote from said coupling, said arrangement comprising a pair of laterally-spaced flexible tension mem ber anchorages mounted on one of said vehicles at a location nearer its remote end than its coupling end, a guide wheel carrier movably mounted for longitudinal travel along the other vehicle at a location nearer its remote end than its coupling end, a flexible tension member guide wheel means rotatably mounted on said carrier, a flexible tension member disposed in an approximately U-shaped path along said vehicles with its free ends secured to said anchorages, said flexible tension member having substantially parallel portions extending from said anchorages along opposite sides of said vehicles and a connecting portion extending between said parallel portions to and around said guide wheel means, and mechanism operatively connected to said guide wheel carrier for moving said guide wheel carrier longitudinally along its respective vehicle.

5 A load-distributing arrangement for tractortrailer vehicles interconnected by a coupling wherein each vehicle has a coupling end adjacent said coupling and a remote end remote from said coupling, said arrangement comprising a pair of laterally-spaced flexible tension member anchorages mounted on one of said vehicles at a location nearer its remote end than its coupling end, a guide wheel carrier mounted on the other vehicle at a location nearer its remote end than its coupling end, a pair of laterally-spaced flexible tension member guide wheels rotatably mounted on said carrier, and a flexible tension member disposed in an approximately U- shaped path along said vehicles with its free ends secured to said anchorages, said flexible tension member having substantially parallel portions extending from said anchorages along opposite sides of said vehicles and a connecting portion extending between said parallel portions to and around said guide wheels.

References Cited in the flle of this patent UNITED STATES PATENTS Number Name Date 1,164,310 Nilson Dec. 14, 1915 1,321,561 Simmons Nov. 11, 1919 1,821,395 Musselwhite Sept. 1, 1931 1,876,498 Hawkins Sept. 6, 1932 2,159,721 Wright May 23, 1939 2,259,923 Byrne et al. Oct. 21, 1941 2,493,874 Hume Jan. 10, 1950 FOREIGN PATENTS Number Country Date 498,399 Germany May 22, 1930 

